As integrated circuit (IC) geometries continue to decrease, and with the advent of Micro-Electro Mechanical Systems (MEMS), the need for reliable, high density packaging solutions increases. A promising solution for providing reliable packaging for chips of continually decreasing size is Wafer Level Packaging (WLP). WLP is a packaging method in which packaging is formed at the wafer level in an IC foundry or other processing location, allowing testing and burn-in to be performed before the dicing of individual chips.
In certain wafer level packaging (WLP) methods, small cavities or enclosures of an IC or MEMS package may be filled with fluid. In many such applications, fluid filling of a WLP may need to be performed in such a way as to prevent bubbles or gaseous pockets from forming in the fluid filled cavities.
Fluid packaging may perform a number of functions essential for an IC or MEMS device. Packaging may provide electrical connection, electrical isolation or passivation from moisture and electrolytes, physical isolation from the environment to provide structural integrity of mechanical devices, thermal and optical protection to prevent undesirable performance changes, and chemical isolation to protect from harsh chemical environments. Electrical connection and isolation may include providing electrical connections from the outside of the MEMS package to electrical or mechanical components of the MEMS device inside the package, electrostatic shielding of the MEMS device, and preventing penetration of moisture and subsequent corrosion of electrical components or undesired interface adhesion. Mechanical protections may provide rigidity allowing mechanical stability throughout the MEMS product life—and may also help prevent undesirable interface stress between dissimilar materials. If the packaging protection is compromised, the MEMS device may fail, producing no output for a given input or producing invalid or inaccurate output for a given input.